In my copending patent application it was pointed out that one can often foresee that a lower marginal part of a tool string must subsequently be disconnected from the remainder of the string and left downhole in the borehole. This is especially so in well completion work, wherein the lower tubing string must sometimes be severed by employment of explosive devices, and the lower string is dropped to the bottom of the hole. An important example of the desirability of separating a tool or pipe string is also found in my issued U.S. Pat. No. 3,706,344, to which reference is made for further background of this invention.
Accordingly, it is desirable to be able to separate a tool string at any predetermined location along its length. It is further desirable that the separation of the string be achieved while avoiding explosives because of the inherent dangers associated with the use of explosive devices, especially when used downhole in boreholes. Moreover, it is especially desirable that the separation of the string be effected by a wireline operation, and that it be brought about in an inexpensive and foolproof manner.